(a) Technical Field
The present invention relates to a thermoplastic elastomer composition having excellent thermal resistance, and more specifically to such a thermoplastic elastomer composition which improves heat resistance, grease resistance and the like of the composition and which can be applied to an automotive constant velocity joint boot and the like. In particular, the thermoplastic elastomer composition increases a hard segment proportion of the thermoplastic elastomer, which comprises a soft segment and a hard segment, and further comprises an amine-based additive.
(b) Background Art
A constant velocity joint boot plays a role of transferring rotational power from a vehicle engine and transmission to the wheels. The joint boot typically includes a joint part made of a bearing for smoothly transferring rotational power, grease at a joint part for reducing friction of the joint part, and a rubber material covering the connecting part. However, long-term durability is not maintained with the conventional rubber material due to a temperature increase around the boot which occurs when a discharge system for high power of vehicles changes.
Further, this reduced durability results in tearing of the rubber of the constant velocity joint boot, which allows the grease to flow out between the torn rubber. This flow of grease, causes a reduction of engine power, a reduction of vehicle lifespan, and an increase of noise under suspension.
In attempt to solve these problems, a heat resistance-improved composition based on a chloroprene rubber has been used. Conventional chloroprene rubber has been extensively used for a constant velocity joint boot due to its excellent grease resistance. However, in order to increase heat resistance of the chloroprene rubber composition, which has a use temperature of up to 100° C., a cross-linking accelerator was added, and a sulfur cross-link was changed to a peroxide cross-link. This increased the temperature range at which the chloroprene rubber composition can be used by about 20° C. Further, in order to secure low temperature flexibility of the chloroprene rubber composition, a plasticizer was further added thereto thereby expanding the temperature range at which the chloroprene rubber composition can be used to about −45˜120° C.
However, although the temperature range at which the chloroprene rubber composition can be used became wider, there was a problem of continuous difficulty of use because the lifespan of the composition is short and variation in lifespan was wide based on external conditions.
Accordingly, it is needed to develop a composition, which can maintain the performance of the constant velocity joint boot even at high temperature, and has excellent performance such as grease resistance, salt water resistance and the like.
The description provided above as a related art of the present invention is just for helping understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.